Multi-well pad drilling has become more and more popular in recent years. Multi-well pad drilling is a method and system for drilling multiple wellbores from a single well pad. As those skilled in the art understand, a well pad is a surface area having one or more wells or well pairs, as well as related equipment thereon. In traditional drilling, only one well is drilled at one site, and the drilling rig has to be disassembled after drilling a well, moved to the next site, and re-assembled therein to drill another well. Compared to the traditional drilling method, well pad drilling accommodates the drilling of multiple wells from one well pad. After drilling a well, the drill rig only needs to move a short distance to the next drilling location in the same well pad to drill the next well, avoiding the need of disassembling, moving and re-assembling drilling rigs between drilling two wells. Compared to traditional well drilling methods, multi-well pad drilling has the advantages of lower drilling cost, shorter completion time for drilling and completing a plurality of wells, and a smaller environmental footprint.
FIGS. 1A to 1G illustrate a conventional well pad system 10, wherein each well pad only comprises one row of production wells and one row of injection wells, straddling a piping and utility corridor. As shown in FIG. 1A, the pad system 10 comprises a Central Processing Facility (CPF) 12 coupled to one or more well pads 14 via pipelines 16. As known in the art, a well pad is a surface area having one or more wells, wellheads and associated processing and transmission equipment. Each of the multiple well pads requires connections to the CPF including communications (such as fibre optics), power, pipelines and access roads.
As shown in FIGS. 1B to 1D, the well pad 14 comprises a plurality of wellhead connection modules 20 coupled to a utility and piping module 22. Each wellhead connection module 20 comprises necessary components 30 such as pipelines, conduits, valves and the like, and is connected to the wellheads of a well pair. Each well pair comprises an injection well 24 for injecting steam or water downhole, and a production well 26 for producing thermally mobilized oil, via suitable natural or artificial lift means. Injection wells 24 may also be used for injecting air such as Nitrogen (N2), water, or gas such as fuel gas or produced gas. Production wells 26 may also be used for producing emulsion, water, gas such as produced gas, or the like.
The piping module 22 also comprises necessary pipelines, conduits, valves, communications, power and other utilities, and couples the wellhead connection modules 20 to the CPF 12. The well pad 10 may also comprise one or more on-site processing facilities 28.
As shown in FIGS. 1E to 1G, in prior-art well pads 14, each pair of injection well 24 and production well 26 form a well pair, with a distance between the injection and production wells 24 and 26 normally about 20 meters (m) to 35 m. Well pairs are spaced laterally by about 10 m. The piping module 22, between the row of injection wells 24 and the row of production wells 26, normally has a width of about 5 m to 7.4 m. The 20 m×10 m spacing has been utilized to date as a typical minimum spacing to facilitate drilling access and accommodation of the infrastructure for each of a plurality of well pairs. Each well pad has been designed with its own infrastructure to manage piping connections for injection and production wells 24 and 26, steam and utility lines, all of which are located between the injection and production wells 24 and 26. Each well pad 14 may have its own layout.
In multi-well pad drilling, as a well pad comprises a plurality of wells, wellheads and related equipment have to be carefully arranged to fit into the well pad and avoid subsurface wellbore collision. Moreover, it is always desired to drill more wells from a single pad to further reduce the drilling cost, completion time and environmental footprint, and to more efficiently consolidate common facilities. It is therefore an object to provide a novel pad drilling method for drilling multiple wells in a well pad and a multi-well pad drilling system employing the same.